Trajectory tracking and traction coordinating controller design for lunar rover based on dynamics and kinematics analysis

Trajectory tracking control is a necessary part for autonomous navigation of planetary rover and traction coordinating control can reduce the forces consumption during navigation. As a result, a trajectory tracking and traction coordinating controller for wheeled lunar rover with Rocker Bogie is proposed in the paper. Firstly, the longitudinal dynamics model and the kinematics model of six-wheeled rover are established. Secondly, the traction coordinating control algorithm is studied based on sliding mode theory with improved exponential approach law. Thirdly, based on kinematics analysis and traction system identification, the trajectory tracking controller is designed using optimal theory. Then, co-simulations between ADAMS and MATLAB/Simulink are carried out to validate the proposed algorithm, and the simulation results have confirmed the effectiveness of path tracking and traction mobility improving

Terramechanics-Based High-Fidelity Dynamics Simulation for Wheeled Mobile Robot on Deformable Rough Terrain

Abstract-Numerical simulation analysis of the motion of wheeled mobile robots is significant for both their R&D and control phases, especially due to the recent increase in the number of planetary exploration missions. Using the position/orientation of the rover body and all the joint angles as generalized coordinates, the Jacobian matrices and recursive dynamic models are derived. Terramechanics models for calculating the forces and moments that act on the wheel-as a result of the deformable soil-are introduced in consideration of the effect of normal force. A rough terrain modeling method is developed for estimating the wheel-soil interaction area, wheel sinkage, and the terminal coordinate. A simulation program that includes the above techniques is developed using Matlab and SpaceDyn Toolbox. Experimental results from a 4-wheeled mobile robot moving on Toyoura soft sand are used to verify the fidelity of the simulation. A simulation example of a robot moving on a random rough terrain is also presented. I. INTRODUCTION HE Sojourner rover and Mars Exploration Rovers (MER) have proven the effectiveness of wheeled mobile robots (WMRs) in planetary exploration missions. Future missions will require the robots to traverse over more challenging deformable rough terrain. Dynamic simulation plays an important role in both the R&D and tele-operation phases of WMRs The dynamics of WMRs is primarily composed of two parts: the multi-rigid-body dynamics of the vehicle and the wheel-soil interaction terramechanics, which is intricate but important for improving the fidelity of a simulation. Some This work was supported by the National Natural Science Foundation of China Due to the differences between WMRs and terrestrial vehicles in terms of physical dimension, wheel shape, payload, terrain, running velocity, and control mode, etc., it is necessary to examine the applicability of conventional terramechanics theory and to improve it by targeting WMRs. Yoshida et al. from the Space Robotics Laboratory (SRL) at Tohoku university have been researching terramechanics for planetary exploration robots [9]. The conventional Wong-Reece terramechanics formula was employed to derive an improved practical model for calculating drawbar pull This study greatly improves the fidelity of the simulation platform developed at SRL by embedding high-fidelity terramechanics models and dealing with the contact between deformable rough terrain and different wheels rather than an entire rover. A generalized dynamics model for mobile robots, considering all the external forces and moments that act on the wheels, is deduced in Section II. A high-fidelity driving terramechanics model considering wheel lug effect and slip-sinkage, as well as a steering model are introduced in Section III. Section IV describes the method for estimating the wheel-soil contact area on deformable soil. Section V presents the simulation implementation, experimental validation, and an example. [ ]( Terramechanics-based High-Fidelity Dynamics Simulation for Wheeled Mobile Robot on Deformable Rough Terrain II. GENERALIZED RECURSIVE DYNAMICS MODELING A. Recursive Kinematics and Jacobian Matrices Jacobian matrix for mapping generalized velocities to the end-points; elements, i.e., linear velocities and angular velocities of the body, and joint velocities. Let ae X and ae J denote the velocities of all the wheel-soil interaction points and the corresponding Jacobian matrix: (1) where a X ( 6 1 v n × ) is the velocity vector of all the centroid, J a (

Fault-Tolerant Control Strategy for Steering Failures in Wheeled Planetary Rovers

Fault-tolerant control design of wheeled planetary rovers is described. This paper covers all steps of the design process, from modeling/simulation to experimentation. A simplified contact model is used with a multibody simulation model and tuned to fit the experimental data. The nominal mode controller is designed to be stable and has its parameters optimized to improve tracking performance and cope with physical boundaries and actuator saturations. This controller was implemented in the real rover and validated experimentally. An impact analysis defines the repertory of faults to be handled. Failures in steering joints are chosen as fault modes; they combined six fault modes and a total of 63 possible configurations of these faults. The fault-tolerant controller is designed as a two-step procedure to provide alternative steering and reuse the nominal controller in a way that resembles a crab-like driving mode. Three fault modes are injected (one, two, and three failed steering joints) in the real rover to evaluate the response of the nonreconfigured and reconfigured control systems in face of these faults. The experimental results justify our proposed fault-tolerant controller very satisfactorily. Additional concluding comments and an outlook summarize the lessons learned during the whole design process and foresee the next steps of the research

Cooperative Path-Planning for Multi-Vehicle Systems

In this paper, we propose a collision avoidance algorithm for multi-vehicle systems, which is a common problem in many areas, including navigation and robotics. In dynamic environments, vehicles may become involved in potential collisions with each other, particularly when the vehicle density is high and the direction of travel is unrestricted. Cooperatively planning vehicle movement can effectively reduce and fairly distribute the detour inconvenience before subsequently returning vehicles to their intended paths. We present a novel method of cooperative path planning for multi-vehicle systems based on reinforcement learning to address this problem as a decision process. A dynamic system is described as a multi-dimensional space formed by vectors as states to represent all participating vehicles’ position and orientation, whilst considering the kinematic constraints of the vehicles. Actions are defined for the system to transit from one state to another. In order to select appropriate actions whilst satisfying the constraints of path smoothness, constant speed and complying with a minimum distance between vehicles, an approximate value function is iteratively developed to indicate the desirability of every state-action pair from the continuous state space and action space. The proposed scheme comprises two phases. The convergence of the value function takes place in the former learning phase, and it is then used as a path planning guideline in the subsequent action phase. This paper summarizes the concept and methodologies used to implement this online cooperative collision avoidance algorithm and presents results and analysis regarding how this cooperative scheme improves upon two baseline schemes where vehicles make movement decisions independently

Path-Following Control of Wheeled Planetary Exploration Robots Moving on Deformable Rough Terrain

The control of planetary rovers, which are high performance mobile robots that move on deformable rough terrain, is a challenging problem. Taking lateral skid into account, this paper presents a rough terrain model and nonholonomic kinematics model for planetary rovers. An approach is proposed in which the reference path is generated according to the planned path by combining look-ahead distance and path updating distance on the basis of the carrot following method. A path-following strategy for wheeled planetary exploration robots incorporating slip compensation is designed. Simulation results of a four-wheeled robot on deformable rough terrain verify that it can be controlled to follow a planned path with good precision, despite the fact that the wheels will obviously skid and slip

Navegación Autónoma de un vehículo Pequeño en Interiores Empleando Visión Artificial y Diferentes Sensores

En este trabajo se presenta una propuesta para la navegación en interiores de un robot pequeño, con arquitectura de vehículo con ruedas. Para la navegación autónoma se implementa un algoritmo de planeación de trayectorias en donde se toma información del entorno para reconocimiento de objetos mediante técnicas de visión artificial y sensores de proximidad para medición y cálculo de la distancia entre el robot y los posibles obstáculos encontrados, de esta forma se recalcula la trayectoria necesaria para evitar choques. Por otra parte, se trabaja la optimización del tiempo y seguridad de navegación, ajustando la velocidad en función de la rugosidad del suelo, a saber: 1) avance rápido en superficies de alta rugosidad, 2) avance lento en superficies de baja rugosidad, posibilitando la disminución del deslizamiento de las ruedas y mejorando el cálculo, por odometría, de la posición del robot dentro de su entorno. Se presentan las técnicas de extracción de características y las arquitecturas y tipos de redes neuronales artificiales empleados tanto para el reconocimiento de objetos como de los tipos de texturas. Se muestran los resultados obtenidos al realizar pruebas de navegación en diferentes entornos en interiores en donde se presentan tanto los tiempos de recorrido como la distancia entre la posición deseada y la posición final del robot. Las pruebas se realizan en la plataforma robótica LEGO Mindstorm EV3.Beca para estudios de posgrado CONACyT No. de cuenta: 153001

Advances in Spacecraft Systems and Orbit Determination

"Advances in Spacecraft Systems and Orbit Determinations", discusses the development of new technologies and the limitations of the present technology, used for interplanetary missions. Various experts have contributed to develop the bridge between present limitations and technology growth to overcome the limitations. Key features of this book inform us about the orbit determination techniques based on a smooth research based on astrophysics. The book also provides a detailed overview on Spacecraft Systems including reliability of low-cost AOCS, sliding mode controlling and a new view on attitude controller design based on sliding mode, with thrusters. It also provides a technological roadmap for HVAC optimization. The book also gives an excellent overview of resolving the difficulties for interplanetary missions with the comparison of present technologies and new advancements. Overall, this will be very much interesting book to explore the roadmap of technological growth in spacecraft systems